1. Field of the Invention
The present invention is generally related to fasteners and in particular to a bolt that is locked into position and prevents the release of loose parts in the event the bolt breaks.
2. General Background
In a variety of situations, especially in nuclear power plants, many bolts are locked in position to prevent loosening and to capture the bolt head to prevent loose parts from entering the system if a bolt should fail. Methods used to capture and lock bolts are to incorporate welded locking cups or bolt heads, staked lock nuts, upset threads, or lock nuts. Methods requiring welding are not acceptable when performing field work on radioactive parts because most of this work must be performed underwater and underwater welding for such an application is unavailable. Patented devices directed toward locking fasteners of which applicants are aware include the following.
U.S. Pat. No. 4,411,570 discloses a tamper-proof fastener where a pin is driven into a bore in the fastener to deflect a fastener leg outwardly and lock it in its installed position. The pin is headless and fits flush with the head of the fastener to prevent tampering.
U.S. Pat. No. 3,042,094 discloses an expander received inside a bolt to cause locking of the threads with the nut.
U.S. Pat. No. 2,438,533 discloses the use of a pin to spread two arms of the stud apart to lock the stud in place.
U.S. Pat. No. 1,409,817 discloses the use of a locking key that causes a slotted end of the bolt to expand and lock with a nut. Separated portions of the key are bendable to prevent separation of the key and bolt while the key head is received in a recess in the bolt head.
U.S. Pat. Nos. 2,871,749; 2,463,859; 322,657 and French Patent No. 867,253 all disclose locking members that are threaded into the bore through the center of the bolt.
U.S. Pat. Nos. 2,314,445 and 2,181,103 disclose smooth unthreaded rivets secured with center-bore drive pins.
U.S. Pat. Nos. 1,372,291; 1,033,120 and 990,065 disclose designs where the locking force is applied from the end of the bolt toward the head.
U.S. Pat. No. 2,370,327 discloses the use of a tubular insert for permanent anchorage in environments where vibrations and ordinary operating stresses may cause loosening.
Although a variety of locking bolts are known in the art, there exists a need for a locking bolt that can be installed and removed by access to only one side of the bolt, that prohibits the release of loose parts if the head of the bolt should separate from the main body portion, and that does not add preload to the bolt which can result in increased bolt failures.